This carb was on a Buick 455 with SP1 intake setup for racing. I'm told this is a 750cfm with an adjuster for going to 950cfm. Adjust a flow Anyone familiar with this? Thanks. IMG_3824 by azstage1 posted Sep 21, 2018 at 8:47 PM IMG_3825 by azstage1 posted Sep 21, 2018 at 8:47 PM IMG_3826 by azstage1 posted Sep 21, 2018 at 8:47 PM IMG_3827 by azstage1 posted Sep 21, 2018 at 8:47 PM IMG_3828 by azstage1 posted Sep 21, 2018 at 8:47 PM
well , #3310 is a common 750 cfm vac sec holley number . so maybe a holley that was prepped by BG or an early BG carb if maybe they used holley basic parts as cores ? early 3310's ( -1 ) had rear metering block , after that no . but the base plate throttle openings look more like 850 size . hard to tell from a pic . 1-11/16" is 650-750 , 1-3/4" is 850 and some bigger stuff . 50cc pump on front is alot normally . oem 850's only used a 30cc . that looks like some kind of early style vac sec opening rate adjuster maybe sticking out of the top of that vac sec assembly , not a cfm adjuster . cfm is not really adjustable . it can be modified but usually just going to a bigger carb is more cost effective and a safer method . unless you have a fully equipped carb shop and a ton of experience .
I just measured the throttle opening on the bottom. they are 1 11/16". Guy I bought it from said he would use the adjuster to slow the car down for certain bracket races or something like that.
the adjuster should move the secondary opening rate rpm . if it works correctly it's a lot handier than taking the cover off and changing springs . there are newer versions out . my guess - etching on side of carb put there when they machined off the choke tower , good for ID purposes . it could be a carb prepped by BG ? it could just be a garden variety 750 with some BG stickers on the bowls ? common carb , and if someone has been inside of it you never really know whats been done . the rear metering block may be stamped #4100 , that's the block number for the rear conversions I normally find . the front block may be marked #10569 (? , memory . i'll check notes) or have a #3310 number on it . if so then at least it has the correct blocks on there and may be a good rebuild candidate if the rest of carb seems ok .
Thanks again for the help. I'm a carb noob. Do you have some kind of reference that labels some of the main parts of these carbs? Rear metering block for example.
i'm sure there is internet/you tube etc info that you can check out . what you are looking for I guess (?) is an exploded view with parts listings . actually some rebuild kit instructions have just that . basically they are a modular carb . base , body , front metering block and fuel bowl , rear fuel bowl and rear metering block if so equipped . if no rear metering block then there will be a metering plate . that's just a real simple version ( cost savings ) of a metering block with preset lower passages that act as jets . no jets to change = no adjustment . you can change plates as they have dif sizes available . sent ya a PM .
